President Trump on Friday signed a memorandum asking the Labor Department to review a contentious rule meant to protect retirement savers from receiving poor investment advice. Out of all the regulations that Trump has taken aim at since taking office, this is the one that could impact consumers’ wallet the most, as it directly impacts the advice brokers give to ordinary investors.

The regulation, known as the fiduciary rule, was finalized last year by the Obama administration and requires brokers working with retirement savers to put their clients’ interest ahead of their own. Critics of the regulation said the rule could limit options for investors and raise costs for financial firms.

“The rule’s intent may be to have provided retirees and others with better financial advice, but in reality its effect has been to limit the financial services that are available to them,” White House press secretary Sean Spicer said Friday. “This is exactly the kind of government regulatory overreach the president was put in office to stop.”

The memorandum asks the Labor Department to evaluate whether the rule harms investors. If officials find that it does, then the administration has the option to rescind or revise the rule. Any changes proposed would need to be put up for public comment.

The Labor Department said in a statement that it will “consider its legal options to delay the applicability date as we comply with the President’s memorandum.”

Trump’s action dealt a major blow to the regulation, which is supposed to take full effect in April. The rule has been in the works for more than six years.

The Obama administration initially proposed a rule in 2010, a victory for consumer groups who longed to make sure all investors received advice that was in their best interest. But the proposal was withdrawn a year later amid intense opposition from Republicans and financial firms. The rule was then held up for years by research, industry meetings and the appointment of a new labor secretary.

By the time the Labor Department finally re-proposed the rule in 2015, it became “unavoidable” that the rule would not take full effect until the next administration, said Barbara Roper, director of investor protection for the Consumer Federation of America, a nonprofit organization that advocated for the rule.

“It was always a gamble,” said Roper, adding that officials had to give financial firms enough time to come into compliance.

Consumer advocates said Friday that they will go to bat for the rule, which is meant to cut down on conflicts of interests in investing advice, such as when a broker may be paid a fee by a third party for selling a particular product. The Obama administration estimated that such issues costs retirement savers $17 billion a year.

“The only people who want to break up the fiduciary rule are the companies who have their hand in your wallet,” said Ed Mierzwinski, director of the consumer program at U.S. Public Interest Research Group.

Some financial firms, however, argue that the rule would hinder their ability to work with certain investors. They caution that the fiduciary rule may require them to move some customers into different accounts. They also say that it may no longer be cost-effective for them to work with investors who have small account balances.

Overall, industry analysts said the rule could lead to sweeping changes in the types of products that retirement savers use and the fees that they pay. Many financial companies said they would make changes to comply with the law, such as lowering investment fees or eliminating commission based retirement accounts.

Financial companies may move some savers into accounts where fees are structured as a percentage of the assets invested. Those may receive less scrutiny under the rule than accounts where brokers are paid based on the type of products they sell. But some critics of the approach say it could raise costs for investors who rarely make trades.

The president’s move comes as the fate of the rule is still being weighed in court. A decision on a lawsuit from major business groups challenging the rule, including the U.S. Chamber of Commerce, is expected any day now.

Correction: A previous version said that the memorandum stalls the fiduciary rule. Instead it asks the Labor Department to review it.